1. Field of the Invention
The invention relates to a power saving method and system adaptable in a Global Navigation Satellite System (GNSS) device.
2. Description of the Related Art
Generally, power saving is always a major concern for GNSS devices. Under some circumstance, the GNSS device does not require aggressive tracking to continuously lock onto its position. FIG. 1 is a flowchart of a conventional GNSS signal reception, in which the correlation channels and processor in the GNSS device are turned off periodically. When the satellite signals are detected to be high quality, efficiency of acquisition and tracking are significantly increased. Experiments show that it is possible to temporarily turn off related components under such a circumstance, with the tracking results remaining unaffected. In step 201, a wake up schedule is configured. The wake up schedule is used to tell the GNSS device to wake up when certain criteria are met. The criteria may comprise a time counter, a trigger from an input device, or signals from a dead reckoning device. A sleep time may be configured to tell the GNSS device of a next sleep time. Thereafter, the GNSS device enters a sleep mode, and a status determination procedure is periodically processed in step 203. Before entering the sleep mode, variables related to the position may be stored in the memory device of the GNSS device. In step 203, the criteria are checked whether the GNSS device should wake up. If so, the GNSS device wakes up in step 205. All the components including the correlation channels, the memory device and processor are initialized and powered on, and the variables are restored for further acquisition and tracking procedures. Upon a next sleep time, the GNSS device enters the sleep mode again in step 207, and the process loops back to step 203.
Since most of the components in the GNSS device are turned off, power consumption is minimized. However, when applied in conditions with rapid variation, undeterminable situations may occur, where a GNSS device in sleep mode may be unable to process. So a more flexible architecture is desirable.